The present specification, drawings and claims relate to fuel evaporative emission control in small internal combustion engines and particularly engines of less than about 50 horsepower (37.2 kilowatts) of the type used for e.g., applications in garden tractors, lawn mowers, generator sets and other portable appliances and marine applications.
Engine applications of the aforesaid type commonly have the fuel tank located proximate the engine for compactness. The fuel tanks employed in such applications usually have a user removable filler cap which contains a vent for permitting make-up air to enter the tank as the fuel is used by the engine. In such applications, the fuel feed is by gravity flow from the tank to the engine carburetor or in some applications by a small fuel pump. Furthermore, in such applications the engine is normally refueled in situ rather than at a refueling station; and, the fuel is poured into the tank from a portable container and quite often with the use of a user-supplied funnel or temporary pouring spout provided with the fuel container.
Recently, it has been mandated that fuel vapor from such small engine fuel systems not be permitted to escape to the atmosphere and that the fuel system including connections to the engine be sealed and prevent emission of fuel vapor to the atmosphere when the engine is not running; and, that when the engine is in operation the fuel vapor be drawn into the engine air inlet.
It is desired to provide for controlling emission in a small engine without requiring complete redesign of the fuel tank and fuel supply system for the small engine. In addition, it is desired to provide for controlling fuel vapor emission in a small engine in a manner which is low in cost and simple to incorporate in mass production of such engines and the appliances into which they are installed. It is further desired to facilitate the incorporation of vapor emission control for small engines with the fuel tank disposed proximate the engine without requiring redesign and retooling for the manufacturer of the tank and the associated components of the engine fuel system.